My Scribbles

When should I use mockObject.Reset() and when should I use mockObject.Invocations.Clear()?

In the context of using a mocking framework like Moq in C# for unit testing, the choice between mockObject.Reset() and mockObject.Invocations.Clear() depends on what you want to achieve.

1. mockObject.Reset():

   • This is specific to the Moq library.
   • It resets the mock object, removing any setups or custom behavior you might have defined for that mock.
   • It does not clear recorded invocations; you can still access them after calling Reset().

   Example:

   var mock = new Mock<MyClass>();
   mock.Setup(x => x.MyMethod()).Returns("Original");
      
   // ... code using the mock ...
      
   // Reset the mock, removing setups
   mock.Reset();
      
   // Now, if you call the method, it won't use the previous setup
   var result = mock.Object.MyMethod();
   

2. mockObject.Invocations.Clear():

   • This clears the recorded invocations on the mock object.
   • It doesn't affect setups or custom behavior. It just removes the history of invocations.
   • This can be useful when you want to verify interactions or check the number of invocations without interference from previous test runs.

   Example:

   var mock = new Mock<MyClass>();
   mock.Setup(x => x.MyMethod()).Returns("Original");
   
   // ... code using the mock ...
   
   // Clear recorded invocations
   mock.Invocations.Clear();
   
   // Now, if you verify invocations, it won't consider previous calls
   mock.Verify(x => x.MyMethod(), Times.Never());

In summary:

• Use mockObject.Reset() when you want to clear setups and start fresh with the mock.
• Use mockObject.Invocations.Clear() when you want to clear the history of invocations, but keep the existing setups and behaviors.

If I set up a method with the same parameters multiple times, the last setup will take effect, right?

In most mocking frameworks, including Moq for C#, the answer is YES. Each new setup for the same method and parameters overrides any previous setups.

Here's an example using Moq:

// Setting up the method with the same parameters but different returns
mock.Setup(x => x.MyMethod()).Returns("FirstSetup");
mock.Setup(x => x.MyMethod()).Returns("SecondSetup");

// Now, if you call the method, it will return "SecondSetup"
var result = mock.Object.MyMethod();